1. Field of the Invention
Embodiments of the present invention generally relate to a pipelayer equipped with a riser cab.
2. Description of the Related Art
FIG. 1 is a front view of a prior art pipelayer 10. The pipelayer 10 is typically used for the construction of underground pipelines which transport hydrocarbons, such as natural gas or gasoline. Typical operation of the pipelayer includes raising, carrying, and lowering heavy pipe 12. The pipelayer 10 is a crawler or tractor-type vehicle having a maneuverable boom 42 disposed on a side thereof. For this reason, the pipelayer 10 is referred to as a sideboom.
The pipelayer 10 further includes a main frame assembly 14 having first and second opposed sides 16 and 18 and a radiator guard 20. The pipelayer 10 includes first and second endless self-laying track assemblies 22, 24, with each of the track assemblies 22, 24 having a roller frame. A rigid cross bar 28 and a pivot shaft connect each track assembly 22, 24 to a respective side 16, 18 of the main frame assembly 14. A pipelayer frame 32 has a first portion 34 secured to the main frame assembly 14 and a second portion 36 secured to one of the roller frames by a plurality of fasteners. The first portion 34 is joined to the second portion 36 by a pin arrangement 40. The boom arm 42 has a first end portion 44, pivotally connected to the pipelayer frame second portion 36, and a second end portion 46 supporting a cable operated load block assembly 48. A drawworks 50 runs a cable 52 in and out to raise and lower the block assembly 48 and the pipe 12. A fluid operated cylinder 54 has a first end portion 56 connected to the pipelayer frame 32 and a second end portion 58 releasably connected to the boom arm second end portion 46. A counterweight 55 is attached to the main frame 14. The counterweight 55 may also be secured to one of the roller frames by a counterweight frame (not shown) similar to the pipelayer frame 32.
The boom arm 42 of the pipelayer 10 cannot rotate without driving the track assemblies 22, 24. To deliver a piece of pipe from the pipe delivery vehicle located on an opposite side of the pipelayer relative to the pipeline trench, the pipelayer would have to drive the track assemblies 22, 24 in order to turn 180 degrees so that the boom would face the pipe delivery vehicle, pick up the pipe, and drive the track assemblies 22, 24 in order to turn 180 degrees so that the boom arm 42 would face the trench in order to deliver the piece of pipe.
Further, the pipelayer 10 is a specialized vehicle. It is not configured to perform other jobs at a pipeline work site, such as excavation. When pipelaying duties are complete, the pipelayer may idle in a yard until required again, which may be a substantial period of time.